Alternating current (AC) rotary electric machines which are used in the function of DC electric generators typically integrate diodes to rectify alternating currents to required DC currents. Alternators (which are intended for charging batteries in starting systems in vehicles or in stationary equipment such as gen-sets or similar) in particular have power diodes connected in rectification circuitry. Semiconductor power diodes work with an unavoidable voltage drop in the range from 0.6 V to 1 V per diode in the forward conducting direction. This voltage drop represents a significant power loss while conducting the generated currents to the battery or to other electrical loads. Consequently, alternators have a rather low operational efficiency, particularly those intended for low system voltages of 14 V or 28 V.
The technical problem to be solved is to provide such a rectifier structure that would allow the rectifier to operate without an outside connection to power supply (usually 12 V) and independently of other electronic circuitry (such as voltage regulators of an alternator). Such a rectifier would eliminate a need for any connection other than the power output to a vehicle installation. In addition, it is desirable for the structure of the rectifier to be configured in a way that it would replace a normal diode rectifier in the same location on an alternator without altering simple air cooling and existing mounting in order not to increase the production costs of the machine.
Using MOSFET transistors preferably of a TOLL type (TO-Leadless Package) with sufficiently low resistance reduces an unwanted voltage drop of 0.6 V-1 V to the range of 0-0.2 V, therefore proportionally also reducing power losses of the alternator and making it more efficient. Mounting transistors in the same place as diodes and not altering the forced air ventilation for cooling allows the remade alternators to operate with a lower working temperature of its critical parts (brushes, rotor rings and bearings), reduces their wearing and consequently increases the life time of alternators. There are a few known solutions to the active rectifier. An example is proposed in the patent publication U.S. Pat. No. 7,292,445 B2 which describes a voltage regulator integrated with an active rectifier for charging the battery more efficiently. The integrated multilayer device is mounted on a separate aluminum base plate with water cooling and the entire assembly is mounted on the side of an existing alternator as an extension which increases its overall diameter. The proposed solution requires a detecting and driving circuitry to be connected to a power supply from the outside.
Another example is proposed in the patent publication US2006151874. The proposed solution is comprised of a power circuit which is controlled by a control part. All power-conducting components of the power circuit are power MOS components and are integrated in a stacked construction which integrates two parallel substrates, between which the power MOS components are placed and with contacts at both sides.
Both of the above examples need a connection to a power supply through a connector and wires in a vehicle harness. This requires an additional installation of wires in the system and introduces a dependency on an outside power supply.